Improvement of critical current density in Fe-sheathed MgB2tapes by ZrSi2, ZrB2and WSi2doping

Fe-sheathed MgB 2 tapes were prepared by the in situ powder-in-tube technique by 5 at% ZrSi 2 , ZrB 2 and WSi 2 doping, respectively. The doping effect of these compounds on the microstructure and superconducting properties of MgB 2 tapes has been investigated by using x-ray diffraction, scanning electron microscope, transport measurements and dc susceptibility measurements. Compared to the undoped samples, J c for all the doped samples were much improved; the best result in terms of J c was achieved for ZrSi 2 doping, by up to a factor of 3.4 at 4.2 K in magnetic fields up to 12 T. Moreover, these dopants did not significantly decrease the transition temperature. The J c – B curves of WSi 2 -doped tapes show better performance in higher magnetic fields in comparison to undoped tapes, suggesting that pinning centres effective in a high-field region were possibly introduced.